ring and pinion pattern check

[sdh148]

Can I get some opinions on this gear pattern? I rebuilt an 8.25 axle with a Yukon Gear 3.21 ring and pinion and new Spicer Trac Loc (Sure-Grip) diff. The official Chrysler/Miller tool for determining pinion shim thickness did not work as described, so I had to do trial and error with a "checking" bearing and gear pattern compound. I ended up using the same thickness shim that originally came out of the axle.
Thanks in advance.

 

[Demonic]

I'm not an expert, but the sharp line at the valley seems too much. Should be softer, no sharp edge. What is your backlash?

Gear Set-Up - Quality Body Shop Drivetrain

 

[A Body 440 WHY NOT]

Looks pretty good to me. Centered nicely. Just my 02

 

[Arron tate]

Can I get some opinions on this gear pattern? I rebuilt an 8.25 axle with a Yukon Gear 3.21 ring and pinion and new Spicer Trac Loc (Sure-Grip) diff. The official Chrysler/Miller tool for determining pinion shim thickness did not work as described, so I had to do trial and error with a "checking" bearing and gear pattern compound. I ended up using the same thickness shim that originally came out of the axle.
Thanks in advance.

Hello sdh148,
May ask where did you get the "New Spicer Trac Loc (Sure-Grip) diff" from ?
Thanks in advance,
Stay Safe....
Happy Mopar
Arron

 

[sdh148]

Hello sdh148,
May ask where did you get the "New Spicer Trac Loc (Sure-Grip) diff" from ?
Thanks in advance,
Stay Safe....
Happy Mopar
Arron

It took me a while to locate one. I had first tried to order from Jegs and Summit, but they don't keep any stock. They just direct ship from the supplier, and my shipment dates kept getting delayed. I found a place that had one on the shelf. Perhaps they have more.
Dodge 8.25 Trac-Lok Differential Posi Carrier Assembly Complete 27 Spline C8.25 1976-1996

 

[Arron tate]

It took me a while to locate one. I had first tried to order from Jegs and Summit, but they don't keep any stock. They just direct ship from the supplier, and my shipment dates kept getting delayed. I found a place that had one on the shelf. Perhaps they have more.

Hello sdh148,
Thanks for the info. I will check them out.
Stay Safe....
Happy Mopar
Arron

 

[my5thmopar]

The gears look new are they? Did you use a new crush sleeve or a sleeve/shims or some other eliminator? What is the backlash and pinion preload? I don't see any carryover in the pattern grease. Did you apply pressure to the ring gear while testing the pattern?

 

[sdh148]

Backlash is .0075" (.006-.008 factory spec) and pinion bearing preload is 28 in-lb (20-35 factory spec).
The gears are new, and I used a new crush sleeve. I applied pressure to the ring gear while testing the pattern.
I'm not sure what is meant by "carryover in the pattern grease."
I do see what you mean by the sharp line in the valley. That could be a concern. I guess I was more focused on centering the pattern between the heel and toe, but, now that I look at the Yukon instruction sheet, it seems that having a nice rounded pattern is more important, even if it is slightly off center.

 

[my5thmopar]

You need to grease several teeth and check. I mean carryover by some grease will get on the clean teeth if you’re applying enough pressure. The pattern looks centered but, I don’t know why you’re not getting good contact. Try putting pressure against the outside edge of the ring gear.

 

[sdh148]

You need to grease several teeth and check. I mean carryover by some grease will get on the clean teeth if you’re applying enough pressure. The pattern looks centered but, I don’t know why you’re not getting good contact. Try putting pressure against the outside edge of the ring gear.

Thanks for the clarification. The pinion had no marking compound (all teeth clean), and I only checked the pattern in this area. To get carryover, I think I would have had to continue rotating the gears until the pinion teeth that ran through the compound contacted the ring gear again. Or, I would have had to mark more ring gear teeth. I did apply pressure while checking the pattern.

Unfortunately, the axle is all reassembled and in the vehicle. I actually did the rebuild in January, and just got the vehicle back on the road following the completion of my other upgrades (springs, shocks, 73-76 UCA/LCA/disc brakes, wheels/tires, etc.). I was asking about the pattern because I am getting some gear whine around 40-45 mph, but only in a very light load/float condition. During normal drive and coast, it is not noticeable, although I haven't yet tested above 50 mph.

 

[my5thmopar]

You don’t put grease on the pinion. I meant more ring teeth and yes keep turning through. Well you most likely won’t get the whine or noise out of it if you have put on more than a few miles. You're new so next time give us that information up front. Good luck

 

[john-9]

your pattern doesn't look too bad --- gear whine is usually caused by incorrect pinion bearing preload -- what did you set your pinion bearing preload at ,,, should have been set with new bearings at 20-25 in/lbs rotating ( pinion only ) or with used bearings 8-15 in/lbs --

 

[sdh148]

your pattern doesn't look too bad --- gear whine is usually caused by incorrect pinion bearing preload -- what did you set your pinion bearing preload at ,,, should have been set with new bearings at 20-25 in/lbs rotating ( pinion only ) or with used bearings 8-15 in/lbs --

New bearings
28 in-lb (20-35 is the factory spec)

 

[sdh148]

This is going to be long winded, but I figured I'd try to list all the details of the ring and pinion setup from day 1.

First, I tried to use the factory service tool, which I bought on ebay, to determine the shim thickness. Unfortunately, the result of this process was a shim thickness over 0.1 inches, which was unreasonable. So, while the tool was useful for installing the bearing cups, it did not work for determining the shim. This meant that I had to use trial and error, so I made some "checking" bearings so I didn't have to press bearings on and off every time. Since the production shim I removed measured .034 (despite being marked "32"), I decided to start with the closest shim from the Motive Gear rebuild kit I bought, which was also .034. Note, maybe I got an incorrect set of shims in the kit, but the kit only included .021, .0295, and .034 shims (multiples of each).

With a .034 shim, I got the following results:

At the time, I thought that looked decent, but, since this was my first time setting up a ring and pinion, I decided to try another shim.

With a .0295 shim, I got the following results:

I thought that this looked pretty similar to .034, but maybe slightly more centered between the heel and toe. Since I though both patterns looked decent, I decided to order Chrysler shims of similar size. The reason for this was that the Motive Gear shims went behind the rear bearing cone, but the Chrysler shim I originally removed was between the housing and rear bearing cup. I figured that this would be easier to change out if I made a mistake. (It is very difficult to get the rear bearing off of the pinion shaft.) So, I ordered Chrysler shims for a Dakota 8.25" axle.

The parts catalog shows that the shim is between the housing and bearing cup, however, Chrysler must have changed the shim location/design over the years, or the parts catalog has an error, because, when I received the shims, they were the same size as the Motive Gear ones, meaning that they went behind the rear bearing cone as well.

So, I chose a Chrysler shim that measured about .0325 and fully assembled the axle with new bearings, crush sleeve, etc.

To be continued...

 

[sdh148]

With the .0325 shim and .0075 backlash, I got the following results:

Six months later, when the vehicle was fully reassembled from other retrofits, I was able to drive it. It was quiet except for during very light throttle conditions, when it had a pretty noticeable whine. So, I wrote the original post looking for suggestions. As Demonic mentioned, the pattern had too much of a sharp line near the root. The Yukon Gear instruction sheet also says that it is more important to center the pattern between the root and the face of the tooth than to center it between the heel and toe. I decided to tear the axle back down and try different shims. I took some pictures of the gear pattern, and it looked pretty much the same as before I drove it. The backlash was also unchanged (I only drove it 10-20 miles.)

.0325 shim .0075 backlash 10-20 miles

To be continued...

 

[sdh148]

Since the only smaller shim I had from the Motive Gear kit was .021, I decided to try that one.
.021 shim, .008 backlash

The drive side is not terrible, but the coast side is way in the corner. Before I tried another shim, I decided to reduce the backlash, just to see if it made any appreciable difference in the pattern.

.021 shim, .005 backlash -- no appreciable difference in the pattern

To be continued:

 

[sdh148]

After locally sourcing a Yukon Gear shim kit at Autozone, I combined two shims to achieve .0255.

.0255 shim, .007 backlash

You can tell that the pattern is moving in the correct direction, but the coast side was still too close to the face of the teeth.

Next I tried .0285.

.0285 shim, .006 backlash

Again, everything moved in the correct direction. The drive side is centered root to face and almost centered heel to toe. Also, the marking has no sharp/dark edges. The coast side is not centered, but the marking is no longer in the corner and has no sharp/dark edges.

Comparing the .0285 to the .0295 shown above, while the .0295 pattern seems more "centered," I think the markings with the .0285 are a bit "smoother," although I'm probably splitting hairs at this point.

I am most likely going to go with .0285. Does anyone have any thoughts (or even read this far)?

Thanks.